I rambled about having things do lots of things
here, but after some comments on one of my Bittercon posts, I feel inspired to expand on this for foreshadowing.
Other things, sometimes you can get away with something that
just advances the plot, or
just characterizes. But set-up and foreshadowing are particularly hard to do. Oh, yes, this is going to be important later -- and there is no suspense about whether it's going to be important later.
Yes, you have to show the gun in Act One to fire it in Act Three. But dumping it in the middle of Act I is clumsy. Have Jack point it out in the first act as his father's, to characterize him.
Come to think of it, this goes double for red herrings. If they serve a purpose -- and a purpose equal to their development -- the reader won't be as frustrated when they don't pan out. When you don't, well, Aristotle skewer it a long time ago:
But of all these ways, to be about to act knowing the persons, and then not to act, is the worst. It is shocking without being tragic, for no disaster follows